1. Field of the Invention
The present invention generally relates to a probe card, in particular, to a probe card having transformers.
2. Description of Related Art
It is required to perform electrical tests for integrated circuit (IC) chips at different stages of the semiconductor manufacture process. The electrical functionalities of each IC chip are ensured through the test of package and wafer. There are two factors contributing to the needs of product tests, which are the new design of chip and the increase in product yields. With the advance in functionalities and complication of chip, the needs for fast and accurate tests become even more important.
Wafer probing is done by forming a test circuit between a test platform and a probe card first, and then let the probe pin of the probe head on the probe card contact the pad or bump on the chip directly. By doing so, the signal in the chip may be collected by contacting the probe head with each chip on the wafer, and the signal is transmitted to the test platform for analysis.
A probe card usually includes a transformer, located between the probe head and the circuit board of the probe card, for the probe head to contact with the circuit board indirectly. Especially, a package substrate may be used as the transformer rather than making another transformer independently with some circumstance in order to reduce the cost of test. However, with the decrease in package size, the package substrate becomes thinner. In other words, if we use the package substrate as the transformer, the transformer also becomes thinner. Thus, bending and warping may occur easily during tests due to the decrease in thickness of the transformer, which impact the structure strength and the test result. In addition, the force exerted on the probe head during tests may be uneven because thinner transformer is not capable of providing strong supporting force. Therefore, how to increase the structure strength of probe card by reforming transformer has become an important issue.